An image-forming apparatus using an electrophotographic method (hereinafter, referred to as an “image-forming apparatus”) mainly includes, for example, an electrophotographic photosensitive member, a charging device, an exposure device, a developing device, a transfer device, a cleaning device, and a fixing device. Steps, such as charging, exposure, developing, and cleaning, are repeatedly performed.
The charging device is configured to charge a surface of the electrophotographic photosensitive member (hereinafter, also referred to as a “photosensitive member”). A contact charging method using a charging member in contact with a surface of the photosensitive member is often used. In this case, a roller-shaped charging member is preferably used.
Toner which has not transferred to a transfer material, such as paper, in a transfer step (hereinafter, also referred to as “residual toner”) adheres to the surface of the photosensitive member, in some cases. To remove the residual toner from the surface of the photosensitive member and permit the photosensitive member to be used for the subsequent image formation process, a cleaning member, such as an elastic blade, used in a cleaning step is often in contact with the surface of the photosensitive member.
The residual toner that has not been removed with the cleaning member affects the subsequent image formation process and can cause a phenomenon in which the quality of an image is reduced. The phenomenon is commonly referred to as a “cleaning failure”. When the phenomenon occurs, a longitudinal streak-like image (hereinafter, referred to as a “longitudinal streak image”) on a solid white background often emerges.
PTL 1 discloses a charging member configured to suppress the occurrence of the cleaning failure by inhibiting the fixation of corona products to a surface of a photosensitive member.